Orthopedic implants for the human knee generally have a femoral and a tibial component. The tibial component is usually placed on the resected proximal surface of the tibia and frequently has a metal baseplate with a shaft extending into the tibial medullar canal. The baseplate usually carries an ultra high molecular weight polyethylene (UHMWPE) articulating surface. The articulating surface has a medial and lateral condyle compartment. A femoral component is implanted on a resected distal end of the femur and presents artificial condyles to articulate with the condyle compartments of the tibial component. A femoral component generally comprises the condyle articulating surfaces and fixation means which may include an elongated stem which extends into the femoral medullar canal of the patient. Such prosthesis are well-known and examples can be found in U.S. Pat. Nos. 4,963,152; 5,062,852; and 5,071,438.
For patients who require an artificial knee prosthesis, degeneration of the bone at either the tibia or femur or both may be occurring. Moreover, this degeneration may be proceeding unevenly with respect to the two condyles. It is also known that some patients require a reoperation and the installation of what is called a "revision" knee prosthesis. The revision knee prosthesis is generally more massive than a so-called "primary" knee prosthesis. The revision femoral knee condylar parts may be thicker and more robust and the medullar shaft may be substantially longer. Moreover, in many cases degeneration of one condyle may be substantially more advanced than the other.
In such cases, it is advantageous to be able to retain as much bone in each condyle as possible. This, however, may result in uneven resection of the condyles. One can compensate for this disparity by providing shims of varying thickness which can be placed on one condyle or the other or both to raise the surfaces in an appropriate fashion.